1. Field of the Invention
The present invention relates to a grinding wheel truing method and a grinding machine.
2. Description of Related Art
In a common grinding machine according to the related art, a truing surface, that is, a surface for reshaping a grinding wheel, of a truer is fixed in position with respect to the grinding machine. Thus, in the case where there is an error in position of a surface to be processed of the grinding wheel in the X-axis direction (a direction in which the grinding wheel cuts into a workpiece and which is orthogonal to the grinding wheel rotational axis) and in position thereof in the Z-axis direction (a direction that is parallel to the grinding wheel rotational axis) due to thermal displacement of the grinding machine or the like, it is necessary to detect the accurate position of the surface to be processed of the grinding wheel in the X-axis direction and the accurate position thereof in the Z-axis direction in order to execute truing of the grinding wheel using the truer. To this end, the grinding machine is provided with an X-axis direction detection pin and a Z-axis direction detection pin, and the grinding wheel is moved finely in the X-axis direction and the Z-axis direction so that the surface to be processed of the grinding wheel contacts the X-axis direction detection pin and the Z-axis direction detection pin in order to accurately detect the position of the surface to be processed of the grinding wheel in the X-axis direction and the position thereof in the Z-axis direction.
Japanese Patent Application Publication No. 2009-285776 (JP 2009-285776 A) describes a grinding device in which at least one of a wheel spindle that supports and rotates a grinding wheel and a dressing spindle that supports and rotates a dresser is supported by a controllable axial magnetic bearing and a controllable radial magnetic bearing that support the spindle in a non-contact manner at a predetermined target levitated position in the axial direction and the radial direction. In this configuration, when a surface to be processed of the grinding wheel is caused to contact a dressing surface of the dresser, the amount of deviation of the dresser or the grinding wheel in the axial direction is detected from variations in value of a control current for the controllable axial magnetic bearing, and the target levitated position of the controllable axial magnetic bearing in the axial direction is changed in accordance with the detected deviation amount to cause the position of the surface to be processed of the grinding wheel in the axial direction to coincide with the position of the dressing surface of the dresser.
In the grinding machine according to the related art in which the position of the surface of the grinding wheel in the X-axis direction and the position thereof in the Z-axis direction are detected using the X-axis direction detection pin and the Z-axis direction detection pin, the position at which the X-axis direction detection pin and the Z-axis direction detection pin contact the surface of the grinding wheel is detected while the grinding wheel is finely moved. Thus, it takes a significantly long time to detect the position of the surface of the grinding wheel, which degrades the efficiency of truing.
In the grinding device described in JP 2009-285776 A, meanwhile, at least one of the wheel spindle and the dressing spindle is constituted by the controllable axial magnetic bearing and the controllable radial magnetic bearing described above, which significantly complicates the structure of the device and increases the size of the device.